1. Field of the Invention
The present invention relates to an air-conditioning apparatus configured to include a plurality of air conditioners. More particularly, the present invention relates to the air-conditioning apparatus that allows the plurality of air conditioners to communicate with each other, although they generally operate individually, to achieve efficient energy saving performance and promote comfort.
2. Description of the Related Art
Air conditioners for business applications are usually installed in large spaces of offices or stores. It is a common practice, in such cases, that a group of air conditioners is operated and controlled by one remote control. An example of this case is disclosed in JP 07-167519 A.
With reference to JP 07-167519 A, a plurality of air conditioners is operated individually based on instructions by a single remote control so that room temperatures reach a set temperature by heating or cooling. There is nothing more than that.
Therefore, an air conditioner installed in a location near an entrance or a window where higher air-conditioning load is required compared to other parts of a room requires high capacity. A high capacity operation results in low efficiency (=capacity/input). Therefore, if the air conditioners are operated individually, then the room temperature becomes nonuniform. This may reduce the overall efficiency of the group of air conditioners.
In addition, the heat exchanger of the outdoor unit of an air conditioner may be frosted during heating when outside temperatures are low, and frosts may grow. Therefore, defrosting is required at regular intervals. A defrost operation is generally performed by running the outdoor unit exclusively by a refrigerating cycle for cooling while the operation of the indoor unit sending warm air into a room is suspended. Since the heating operation is thus temporarily stopped for defrosting, room temperatures are reduced. Furthermore, those air conditioners may reach a point to start defrosting almost simultaneously since they are controlled to start heating operations simultaneously as a group. If the group of air conditioners warming a room together perform their defrost operations all at once, then a serious reduction in room temperatures may create less comfort.
In addition to that, a low-load cooling operation may be performed in a rainy season or the like when the discomfort index is high because the temperature is not so high but the humidity is high. In such a low-load cooling operation, each air conditioner operates at a high evaporation temperature and a high sensible heat ratio (sensible heat capacity/full capacity) during cooling, i.e., an operation with low dehumidification capacity. Therefore, room air is not sufficiently dehumidified, which cannot improve comfort. Then, if the set temperature of room air is lowered for more comfort, then the power consumption is increased and above all the user of the air conditioner would feel cold. This creates less comfort.